1. Field of the Invention
This invention relates to a novel polyester resin composition suitable for preparing a powder paint.
2. Description of the Prior Art
Powder paints have been recently developed to overcome the disadvantages of solvent-type paints that, when used, volatilize organic solvents harmful to humans into the atmosphere, and are now regarded as a non-environmental polluting paint. Furthermore, the powder paints have various advantages in that coatings having a thickness of about 40 to 200 .mu. can be formed by one coating, that the recovery and reuse of the powder paints are possible, and that high coating yields can be obtained. A powder paint has these advantages, and the demand for a powder paint has rapidly increased in recent years.
It is well known from East German Pat. No. 55,820 that a powder mixture of a polyester having terminal hydroxyl groups with a polyisocyanate blocked with phenol can be applied to a substrate by an electrostatic spray coating or fluidized bed coating, and cured by heating, thereby forming coatings.
However, the cured coatings obtained by heating the powder mixture not only lacks smoothness due to formation of bubbles and insufficient heat flow due to the dissociated phenol, but also often exhibits only an insufficient reactivity even in the presence of a catalyst. Furthermore, the dissociated phenol is very harmful, and the necessity for its removal and recovery also offers a practical disadvantage.